Semaglutide vs. Tirzepatide: Which GLP-1 Prescription Is Right for You?

Semaglutide and tirzepatide are both GLP-1 receptor agonists used for weight loss, but they’re different molecules with different mechanisms, different clinical profiles, and different practical considerations. Here’s how they compare.

Mechanism of Action

Semaglutide (Ozempic, Wegovy, Rybelsus) targets GLP-1 receptors only. It’s a single-agonist medication.

Tirzepatide (Mounjaro, Zepbound) targets both GLP-1 and GIP receptors. This dual-agonist approach activates two incretin pathways simultaneously, which appears to produce greater weight loss and blood sugar control.

Weight Loss Efficacy

Head-to-head data isn’t available yet, but comparing across trials: semaglutide 2.4 mg (STEP 1) produced average weight loss of approximately 15–17% of body weight. Tirzepatide at maximum dose (SURMOUNT-1) produced approximately 20–22%. Tirzepatide appears to produce approximately 5 percentage points more weight loss, though individual responses vary significantly.

Side Effect Profile

Both medications share GI side effects: nausea, diarrhea, constipation, vomiting. However, tirzepatide may have slightly lower nausea rates at equivalent efficacy levels. In SURMOUNT trials, nausea affected approximately 24–31% of tirzepatide users, compared to 40–44% of semaglutide users in STEP trials. The medications weren’t tested head-to-head, so direct comparison is imperfect.

Availability and Cost

Semaglutide: Available as brand-name (Wegovy injection, Rybelsus oral) and compounded (injectable, sublingual, tablet). Compounded semaglutide is widely available from $149–$299/month.

Tirzepatide: Available as brand-name (Zepbound injection) and compounded (injectable, oral). Compounded tirzepatide is typically $50–$100/month more expensive than semaglutide.

How Physicians Choose

Many physicians start with semaglutide because it has a longer clinical track record, broader insurance coverage, and more affordable compounded options. They switch to tirzepatide if the patient plateaus on semaglutide, doesn’t achieve adequate weight loss at maximum dose, or tolerates semaglutide poorly and may respond better to the dual-agonist mechanism. Some physicians start with tirzepatide when maximum weight loss is the primary clinical goal.